Microsurgery, in which a medical surgical microscope is used to observe affected parts while performing surgery, has been studied and introduced in the surgical operation field.
In such microsurgery, a stand is needed to install weighty objects, i.e., a surgical microscope with its attached devices; place them in a desired space; then maintain their position.
Generally, in such a stand, the middle part of a link unit using a parallel link is rotatably connected to a holding unit, while a surgical microscope is installed at one end of the link unit and has a balanced structure having a counterweight which is installed at the other one end of the surgical microscope to counterbalance a weight of the surgical microscope around a rotation point.
Since accessories, such as an assistant scope or a video camera, etc., are installed in the surgical microscope, an overall balance adjustment operation is carried out by changing a position of the counterweight according to its weight such that the surgical microscope and the counterweight are balanced.
However, in case when the surgical microscope and its attached devices remain in the desired position, their vertical balance needs to be maintained. However, a conventional stand has difficulties in controlling the vertical balance since the total weight of the surgical microscope is inconsistent due to the presence and absence of various attachments.